Some known methods for improving the security of a document, such as a passport or other identity document, utilize materials which are visible only in the presence of ultraviolet (UV) light. Such materials have been added to certain inks used for security printing to print UV-visible indicia onto a document, whereby the average person viewing such document would be unaware that such indicia is present on the document but a knowledgeable person (e.g. a customs officer) would inspect such document under UV illumination to identify such indicia for purposes of assessing the authenticity of the document. The known devices used in the identification of such covert UV printed indicia comprise UV fluorescent tubes which emit UV illumination. In use, a document to be inspected is placed under the UV illumination emitted by such a device so that any covert UV-visible indicia on the document is caused to fluoresce with a visible light (i.e. is made visible to an inspector's eye). Disadvantageously, however, such devices are passive only, in that they simply serve to illuminate a specific area; they are themselves unable to read (i.e. via an automated process so as to interpret) invisible indicia which has been printed by means of a UV fluorescent ink. Instead, a user of such known devices is required to manually view and personally interpret the resulting image in order to determine whether the document comprises any covert indicia. Moreover, UV fluorescent tubes have a lengthy stabilization time and, therefore, they are unable to accommodate any high speed processing application such as would be required by an automated device for reading UV-ink printed indicia. Moreover, such tubes are inherently unstable (and, thus, unreliable) because the peak wavelength of the illumination they produce typically varies over time.
There is a need, therefore, for a document reader which operates on an automated basis for relatively high speed processing of security documents having matter associated therewith which is visible only when illuminated by UV or IR light. Further, there is a need for a document reader which is able to read such covert UV-ink (or IR-ink) printed indicia on a full-page basis. There is also a need for such a reader which is able to illuminate one or more predetermined surface areas of a document with light whose frequency or frequency band is/are within one of the infrared, visible and ultraviolet light frequency bands, depending on the particular indicia on such areas of the document which is to be read, and to switch rapidly from one such frequency or band to another. Still further, there is a need for a document reader which is able to automatically read and interpret such indicia. Moreover, there is a need for such a document reader comprised of solid state components enabling a reduction or elimination of moving parts.